Al-Kāfi
Hadith 1434 13ـ عِدَّةٌ مِنْ أَصْحَابِنَا عَنْ أَحْمَدَ بْنِ مُحَمَّدٍ عَنِ ابْنِ أَبِي نَصْرٍ قَالَ كَتَبْتُ إِلَى ابي جعفر (عَلَيْهِ السَّلام) الْخُمُسُ أُخْرِجُهُ قَبْلَ الْمَئُونَةِ أَوْ بَعْدَ الْمَئُونَةِ فَكَتَبَ بَعْدَ الْمَئُونَةِ.
13. A number of our people has narrated from Ahmad ibn Muhammad from ibn abu Nasr who has said the following. “I wrote to abu Ja‘far (a.s.), “Is al-Khums paid before or after deducting the expenses?” He wrote back in answer, “It is paid after the deduction of the expenses.”